Serum growth hormone-binding protein is unchanged in adult panhypopituitarism.

Abstract

The role of GH in regulating GH-binding protein (GHBP) and GH receptor concentrations in humans is not clear. Studies performed mostly in children and on a minor scale in adults are somewhat controversial. The key question as to whether GHBP levels are altered in hypopituitarism before GH treatment is instituted remains unanswered. In this study, we have selected a severely GH-deficient group of adult patients with panhypopituitarism, acquired as a result of surgery and irradiation of hypothalamic-pituitary tumors, to evaluate the GHBP/receptor status by measuring GHBP activity in plasma. Twenty panhypopituitary patients (8 males and 12 females; age range, 20-74 yr) and 20 age (22-68 yr)- and sex-matched normal subjects were studied. GH deficiency was confirmed by insulin-induced hypoglycemia and arginine infusion tests; the peak GH response was less than 2 micrograms/L. Plasma insulin-like growth factor-I levels were below or in the low normal range (mean +/- SD, 88.3 +/- 53.6 micrograms/L) and were significantly different from insulin-like growth factor-I (IGF-I) levels in the normal group (mean +/- SD, 189 +/- 49.8 micrograms/L; P < 0.01). Plasma GHBP activity, measured using a GH-binding/gel chromatography assay, showed similar values in the GH-deficient group (mean +/- SD, 14.1 +/- 3.83%) and the control group (mean +/- SD, 13.7 +/- 3.79%), with no statistically significant difference. Neither the intra- nor intergroup comparison of GHBP levels according to age and sex showed statistically significant differences or age trends. In the light of these data and considering that GHBP activity in plasma probably reflects the GH receptor status in tissues, we may assume that the GH receptor was unaffected by chronic GH deficiency. These findings also support the previously reported concept that the GHBP/receptor level is a relatively fixed determinant of growth, established individually and independently of GH secretory status in early life, perhaps on a genetic basis.

A simple, rapid immunometric assay for determination of functional and growth hormone‐occupied growth hormone‐binding protein in human serum

“…In this study GHBP levels were increased in GHD patients and decreased in acromegalic patients. The disagreement in the reports of GHBP in these two conditions might partially be due to the small number of patients [4,8,11,28,29], but also to the use of different Serum concentrations of GH, GHBP, and GH/GHBP complex in four acromegalic, three GHD patients and four healthy volunteers. The GH/GHBP complexes were determined with increasing amounts of rhGHBP added to the sera.…”

“…There are widely varying levels of the GHBP in human serum [3][4][5] and some disagreement on GHBP concentrations in different metabolic states, e.g. varying GH levels [6][7][8][9][10][11][12]. Interlaboratory comparisons are difficult because of the use of different calibrators.…”

The diagnosis of severe growth hormone deficiency in elderly patients with hypothalamic–pituitary disease

“…GHBP is a high‐affinity binding protein for GH, and GHBP levels have been found to be low in GH‐deficient children (Postel‐Vinay et al ., 1993). In hypopituitary adults GHBP levels have been reported as normal (Davila et al ., 1994), a finding confirmed by this study. The GHBP level may, however, have a role in predicting an individual response to GH replacement therapy, those with low GHBP levels appearing to benefit more from treatment (Johannsson et al ., 1996b).…”

Growth hormone distribution kinetics are markedly reduced in adults with growth hormone deficiency

“…38 Low GHBP levels might reflect a reduced GH receptor density and a concomitant GH insensitivity. 37 A reduced GH clearance by its receptor might explain the delayed GH elimination kinetics in GH-deficient patients, although the possibility of additional mechanisms contributing to this slowed removal is not excluded. However, a similar question has been addressed in the study developed by Veldhuis et al, in a more general sense.…”